It was with great joy that I received the invitation to present this year's Marjory Stephenson Memorial Lecture to pay tribute to one of the outstanding pioneers of microbial chemistry and I would like to thank the Society for this honour. For me it is a special privilege, as I was the last overseas student she accepted prior to her untimely death in the latter part of 1948. I have always regarded myself as being one of the very fortunate microbiologists to have known her and I have deeply regretted that it was not for a longer period of time. As an undergraduate in far-off Australia, her name was the hallmark for excellence in all matters microbiological and biochemical and Marjory Stephenson's Bacterial Metabolism was our 'bible'. It was cause for great excitement when I was awarded a CSIRO Studentship and accepted, as she wrote, 'for one of the two places reserved in our course for postgraduate students'. With bags and books packed, I embarked on the long journey from Sydney to Cambridge. In those pre-jet days the sea voyage to London took five weeks and it was that time of the year when many students and actors from Australia were heading off for the 'old country' to take up their scholarships and broaden their horizons. With such a mix of stage and science the voyage was rarely dull but we all eagerly awaited arrival and the experiences that lay ahead. The attractions and scientific exhilaration of Cambridge were so great that my stay became an extended one, thanks to Ernest Gale's hospitality as Director of the MRC Unit for Chemical Microbiology (later the Sub-Department of Chemical Microbiology, Department of Biochemistry) and his stimulus, enthusiasm and interest in the mysteries of the functioning of the bacterial surface. The brevity of my personal contact with Marjory Stephenson was fully compensated for by the enduring association with Ernest Gale and his colleagues in what was affectionately known as 'the bug hut'. Interest in the bacterial cell surface goes all the way back to the birth of microbiology with the microscopic observations of Antony van Leeuwenhoek recorded in his letters to the Royal Society in 1676. Leeuwenhoek not only described the principal shapes of bacteria but also noted that he was unable to see the surface 'film' which held them together, thereby anticipating the existence of structural components of the cell responsible for their characteristic shape. Much of the ensuing evidence on the existence and nature of a cell wall or membrane in bacteria was indirect, fragmentary and inconclusive. About the mid to late 1940s there was a renewed interest in the bacterial surface, stimulated by transport studies such as those of Gale & Taylor (1947) on the accumulation of amino acids across the permeability barrier of Gram-positive bacteria and the direct visualization of walls and membranes in disrupted and bacteriophage-lysed cells by electron microscopy (Mudd & Lackman, 1941 ; Mudd et al., 1942; Wyckoff, 1948). Indeed, the first Symposium held by this Society in 1949, 'The Nature of ...